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REMOTE SENSING > FINAL > Flashcards

FINAL Flashcards

1
Q

UAS stands for

A

Unmanned Aircraft Systems

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2
Q

A UAS consists of

A

1) an aircraft with no pilot on board,
2) a remote pilot station, 3)
a command and control link, and
4) a payload specific to the intended application/operation

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3
Q

Other names for UAS

A

drone
Unmanned Aerial Vehicle
Remotely Piloted Aircraft System
Unmanned Aerial System (less common)
Unpiloted Aircraft System (less common)

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4
Q

A UAS for civil applications is commonly referred to as a small unmanned aircraft system (sUAS) weighing less than

A

55 pounds

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5
Q

the two types of sUAS

A

Fixed-wing
Multirotor

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6
Q

Fixed-wing drones have better _____ but are __________

A

battery efficiency, harder to fly

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7
Q

Multirotor drones fly by

A

changing the speed of the rotors so that the thrust generated is greater than, equal to or less than the forces of gravity and drag acting on the aircraft

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8
Q

The ______ regulates the rules for small UAS operations under 14 CFR 107

A

FAA

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9
Q

The maximum allowable altitude for UAS is

A

400 ft

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10
Q

Maximum speed for UAS is

A

100 mph

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11
Q

Effective 2021, FAA now requires most UAS to be equipped with

A

remote ID

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12
Q

How long is UAS certificate of registration good for

A

3 years

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13
Q

To operate the controls of a UAS, you need a __________ or ____________

A

remote pilot certificate, be under the direct supervision of a person who holds such a certificate

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14
Q

There are two checklists for flying a UAS, one to be done ______ and the other to be done ________

A

before going out to fly, before taking off

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15
Q

The first item on the pre-going out to fly checklist is

A

Check the NOAA Aviation Weather Center website for weather conditions

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16
Q

A best practice for capturing quality drone data is _________ because __________

A

Fly within 2 hours of local solar noon, Shadows are the shortest and solar radiation intensity is the highest
Note: 12 pm is NOT solar noon

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17
Q

Drone images should have _____ % overlap

A

75

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18
Q

True or false, ALL aerial images contain geometric distortions

A

True

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19
Q

Ways that aerial images can be distorted

A

Shape
Size
Scale

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20
Q

Geometric distortions are created due to _______ errors and _______ errors

A

systematic, random

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21
Q

Examples of Systematic Distortions are

A

Earth rotation
Earth’s curvature
Atmospheric refraction
Topographic effects
Relief displacement

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22
Q

Examples of Random Distortions are

A

Changes in flight altitude
Changes in flight attitude (roll, pitch, yaw)
Changes in velocity

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23
Q

Relief displacement

A

Tall objects are displaced away from the center of the air photo

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24
Q

Geometric Correction

A

putting pixels in their proper planimetric (x, y) map locations i.e. real-world coordinates referenced to a map projection

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25
Q

A geometrically corrected image is often referred to as

A

an orthophoto

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26
Q

Geometric correction of an air photo is also known as

A

Georeferencing
Georectification
Image-to-map rectification
Geometric transformation

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27
Q

Geometric correction requires 4 basic steps:

A

1) Choose a source
2) Select ground control points (GCPs)
3) Image transformation
4) Accuracy assessment

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28
Q

The best source for georeferencing is

A

Google Earth Pro

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29
Q

Examples of Good GCPs

A

building corners, street corners, large trees, landmarks

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30
Q

Examples of Poor GCPs

A

cars, rocks, shoreline of a beach, center of a field

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31
Q

GCPs must be distributed…

A

evenly across the unreferenced image, starting from edges and working towards the center

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32
Q

A minimum of ___ GCPs is required

A

3

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33
Q

More GCPs =

A

better fit

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34
Q

Accuracy Assessment incorporates

A

the total root mean square error (RMSE)

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35
Q

The lower the overall RMSE,

A

the better the fit is

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36
Q

_______ is the most important physical quantity in remote sensing

A

Radiance

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37
Q

Radiance indicates

A

how much of the energy emitted, reflected, transmitted or received by a surface will be finally received by a remote sensor

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38
Q

Remote sensors measure radiance in a different range of wavelengths and then convert radiance signals to

A

digital numbers (DNs)

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39
Q

The DN of each image pixel corresponds to

A

the average radiance measured electronically over the ground area corresponding to that pixel

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40
Q

Theoretically, there is a ________ between radiance measurements and surface reflectance

A

direct linear relationship

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41
Q

reflectance

A

proportion of radiation reflected from surface objects relative to the total amount of incident energy

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42
Q

The ____ - ____ relationship can be used to perform radiometric calibration for air photos

A

radiance-reflectance

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43
Q

Assumptions of Empirical Line Calibration

A

the darkest object in an image does not reflect or emit any radiation. DN = 0 represents rλ = 0.
the brightest object in an image does not saturate DN (DN < 255)
radiance measurements made by a sensor have a perfect positive linear relationship with surface reflectance

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44
Q

The pinhole camera was later replaced by
the

A

simple lens camera

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45
Q

The simple lens camera introduced the adjustable

A

diaphragm and shutter

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46
Q

A diaphragm (a.k.a. aperture stop) controls…

A

the amount of light reaching the film

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47
Q

A shutter is a device that

A

allows light to pass for a determined period

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48
Q

The camera lens is an optical device that

A

consists of a curved (convex) material that allows light to pass through. The lens bends the light, reassembles the light reflected from the scene, and forms an image on the sensor

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49
Q

the process called focus

A

Moving the lens closer or further from the sensor to channel the light to recreate the image clearly

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50
Q

focal length

A

the distance from the lens at which parallel light rays are focused to a point

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51
Q

Shutter controls the duration of exposure (t), also known as

A

shutter speed

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52
Q

Diaphragm controls the diameter (d) of the lens opening during exposure, also known as

A

aperture

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53
Q

Exposure is the amount of…

A

energy exposed onto the sensor per unit sensor area

54
Q

In photography, aperture is expressed in f-numbers, known as

A

f-stops

55
Q

A small fstop (e.g., f/1.4) means a

A

large aperture (wider opening), while a large f-stop (e.g., f/32) means a small aperture (smaller opening)

56
Q

Aperture size has a direct impact on the ______ of a photograph

A

brightness

57
Q

A smaller f-stop allows _________ into the camera

A

more light

58
Q

Depth of Field (DoF)

A

the range of distance of the image that appears acceptably sharp

59
Q

A small f-stop (e.g., f/1.4) makes the foreground objects ______ but the background ______

A

sharp, blurry

60
Q

A large f-stop (e.g., f/32) aka small aperture brings _______ in focus

A

all foreground and background objects

61
Q

True/false, both aperture and shutter speed control the amount of light that comes into the camera

A

True

62
Q

A slower shutter speed lets in ______ light into the camera

A

more

63
Q

units for aperture

A

f-stops

64
Q

units for shutter speed

A

seconds

65
Q

If the shutter speed is slow (e.g., 1/2 s), it can create an effect called

A

“motion blur”, where moving objects appear blurred along the direction of the motion

66
Q

With longer shutter speed, images appear brighter/darker?

A

brighter

67
Q

A fast shutter speed ______ the action in the image

A

freezes

68
Q

ISO

A

the camera’s sensitivity to light

69
Q

A lower ISO value means ______ sensitivity to light, while a higher ISO means ______ sensitivity

A

less, more

70
Q

ISO is a camera setting that will

A

brighten or darken a photo

71
Q

As the ISO number increases, the photo will become

A

progressively brighter

72
Q

True/false, A photo at ISO 400 is twice brighter than ISO 200

A

True

73
Q

True/false, You should only raise your ISO when you are unable to brighten the photo via shutter speed or aperture instead

A

True

74
Q

A photo taken at too high of an ISO will

A

show a lot of grain

75
Q

when a high ISO is necessary

A

when you really need to freeze the action in a photo and therefore need a fast shutter speed

76
Q

The aperture value and shutter speed are ________ proportional

A

inversely

77
Q

True/False, In aerial photography for remote sensing and photogrammetry purposes, the rule of thumb is to slightly underexpose your photos

A
78
Q

True/False, Overexposure is irreversible

A

True

79
Q

Filters are

A

transparent materials that, by absorption or reflection, eliminate or reduce the energy reaching a film in selected portions of the spectrum

80
Q

A low-pass filter

A

allows lower wavelengths to pass through but blocks higher wavelengths

81
Q

A high-pass filter

A

absorbs energy below a certain wavelength

82
Q

A band-pass filter

A

absorbs all other wavelengths except a specific band

83
Q

A band-stop filter

A

absorbs energy for a specific range of wavelengths but allows other wavelengths to pass through

84
Q

a ______ filter is the most popular colored filter used for black and white photos

A

yellow

85
Q

A single-lens camera uses ______ bands

A

wide

86
Q

A multi-lens camera uses ______ bands

A

narrow

87
Q

Bands on a ______ camera suffer from data contamination from neighboring bands

A

single-lens camera

88
Q

Photogrammetry is

A

the science and technology of obtaining reliable spatial measurements and geometric information about surface objects and phenomena

89
Q

True/False, Remote sensing deals with 2D satellite imagery whereas Photogrammetry not only works on 2D imagery, but also more complex 3D models

A

True

90
Q

True/false, Photogrammetry uses an imaging system rather than collecting data in different wavelengths

A

True

91
Q

two main branches of Photogrammetry

A

metric and interpretive

92
Q

Metric Photogrammetry

A

makes precise measurements and evaluates exact sizes, shapes, positions, distance, angles, areas, volumes, and elevations of surface features

93
Q

Interpretative Photogrammetry

A

deals in identifying surface objects and judging their significance

94
Q

Aerial photographs are classified as either

A

vertical or oblique

95
Q

Vertical photo

A

an aerial photo taken by a camera looking straight down at the ground

96
Q

Oblique photo

A

an aerial photo taken at an angle

97
Q

Low oblique photo

A

the horizon is not shown

98
Q

High oblique photo

A

the horizon is always visible

99
Q

Nadir

A

the location on the ground that lies directly below the camera

100
Q

Principal Point

A

the center of a vertical photo – found by the
intersection of lines connecting opposite and diagonal fiducials

101
Q

Nadir is equal to Principal Point in what type of photos

A

vertical

102
Q

True/False, in oblique photos, it’s possible for the nadir to not be shown

A

True

103
Q

Why when elevation changes, the distance between a-b appears shorter than the distance between c-d (higher elevation) on the photo

A

Relief Displacement

104
Q

Relief displacement is the

A

shift in an object’s image position caused by its elevation above a particular datum

105
Q

If an air photo is ________, the displacement of objects in the air photo is in a direction radial from the principal point (or nadir)

A

vertical

106
Q

All matter with a temperature greater than absolute zero (0 K) emits

A

thermal energy, or heat

107
Q

Thermal radiation is generated when

A

heat from the movement of charges in the material is converted to EMR

108
Q

The ______ the particles move, the greater the kinetic energy and the greater the object’s thermal radiation

A

faster

109
Q

Temperature is the

A

measure of the average kinetic energy of the particles in a substance

110
Q

True/False, All objects on Earth’s surface emit thermal radiation

A

True

111
Q

Why we can use thermal sensor to measure an object’s surface temperature

A

There is a direct relationship between temperature and the amount of TIR energy emitted per unit area

112
Q

Why does TIR band imagery have a lower spatial resolution than visible and NIR band imagery?

A

thermal uses longwave energy, so there is less energy for the sensor to pick up. TIR sensor needs a larger IFOV to ensure enough energy reaches the sensor in order to make reliable measurements

113
Q

what is directly measured by a TIR sensor

A

M, or the energy that an object emits per unit area

114
Q

why the calculation of LST is much more complicated than the Stefan-Boltzmann Law equation

A

Need to calculate emissivity

115
Q

The emissivity, ε, of a surface material is

A

its effectiveness in emitting energy as thermal radiation

116
Q

a blackbody has an emissivity of

A

1

117
Q

Real objects radiate less thermal radiation than a
blackbody and therefore are called ________

A

graybodies

118
Q

Emissivity is the ratio of the thermal radiation emitted from a surface material to the radiation from a _________ at the same temperature

A

blackbody

119
Q

To calculate LST using Ladsat/MODIS/ASTER imagery, you need to know the

A

Multiplicative Scale Factor and Additive Offset

120
Q

Cause of urban heat island

A

Building materials absorb long wave radiation during the day
and have lower rates of radiant cooling during the night

121
Q

Urban Heat Island (UHI) Effect

A

urban areas have higher temperature in comparison to the surrounding rural areas

122
Q

Boundary layer UHI is measured by

A

weather balloons

123
Q

Surface layer UHI is measured by

A

rooftop weather station

124
Q

Canopy layer UHI is measured by

A

weather station at 2-m above the ground

125
Q

Surface UHI is measured with

A

remotely sensed thermal infrared imagery

126
Q

yellow has no

A

blue

127
Q

magenta has no

A

green

128
Q

cyan has no

A

red

129
Q

Depth of Field (i.e. how much of image is sharp) increases as _________ increases

A

aperture

130
Q

All the objects in an aerial photo need to be in focus, which means a ______ aperture/______ f-stop should be used

A

small, large

131
Q

The DLS sensor on a drone _______ so that ________

A

collects incoming solar radiation, radiance can be converted to reflectance

132
Q

First item on pre-takeoff checklist

A

Place the UAS on a flat surface and make sure there is no dirt, rock, and debris underneath the UAS

REMOTE SENSING (2 decks)

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